A conventional frame for an in-line roller skate is generally formed by several ways. The first is that a frame consists of a plurality of aluminum plates which are formed by pressing and then assembled together by screwing. This way has the disadvantages that it is relatively laborious concerning the assembly of the frame, the formed frame has a relatively poor stability, and the connection of the pressed aluminum plates by screwing may loosen after the in-line roller skate has been used for a period of time.
The second is that a frame is formed by a plastic molding; for example, a Polycarbonate (PC) molding has two side wall portions which are connected together by being screwed and spaced apart a fixed distance by spacing rods. The frame formed this way has a better stability than the first.
The third is aimed to improve the second. The third is an integral plastic molding; for example, a Polycarbonate (PC) molding to integrally form the frame for the in-line roller skate.
However, for the following reasons, the second and third ways for forming the frame have their disadvantages in nature: the molding conditions are very complicated and critical to the performance of the frame; if the molding conditions (for example, the molding temperature) have even a minor variation, the obtained frame may not have sufficient strength to withstand an impact acting thereon. Furthermore, a plastic frame does not have a satisfactory structural rigidity.
Thus, a fourth way for forming the frame is suggested. The fourth way uses an extrusion molding of aluminum alloy to form the frame. FIG. 1 of the present application shows a profile of a frame 80 (indicated by thick phantom lines thereof) in accordance with the fourth way. In forming the frame 80, the fourth way is first to extrude a stock of aluminum to become a blank with two side walls 84 (only one is shown) which have a generally rectangular shape and three webs 81, 82 and 83 connecting the two side walls 84 together. Then a material removing operation (for example, milling) is performed on the blank to obtain the shown frame 80, which has a front sole attaching portion and a heel sole attaching portion having a level higher than that of the former. By this design the front and heel sole attaching portions have different levels and the in-line roller skate can have a better operability. However, by a single operation of extrusion molding, it is impossible to form the frame 80 to have the two sole attaching portions having different levels.
Although the frame 80 formed by the fourth way can have an excellent rigidity, stability and operability for the skate, the fourth way has a disadvantage that the machining of the extruded blank into the frame 80 requires a lot of laborious work, which causes the frame 80 to have a relatively high cost of manufacturing, which, in turn, causes the in-line roller skate incorporating the frame 80 to have an unacceptable high price.